What causes mental illness? Could various mental disorders stem from a single underlying cause?
Psychiatrist Christopher M. Palmer explores the intriguing possibility that all mental illnesses might share a common origin. He presents compelling evidence that, despite the complexity of mental illness, the root cause might be rather simple.
Keep reading for Palmer’s groundbreaking ideas about what causes mental illness and how they could reshape our approach to mental health.
What Causes Mental Illness
Palmer says we need a new theory for mental illness. He explains that our current understanding of mental illness is far from complete: We’ve identified only risk factors—characteristics that put someone more at risk of developing a mental disorder—but we still don’t understand what causes mental illness. Without knowing the cause, we can treat only symptoms—not the illness itself.
(Shortform note: Our current understanding of what causes mental illness remains incomplete partly due to insufficient funding for research. Only about $3.7 billion is spent annually on mental health research worldwide; in contrast, both cancer research and infectious disease research receive more than twice that amount. Furthermore, the distribution of the limited resources for mental health research is unbalanced, with over half going to basic research (which might include discovering risk factors, for instance) while studies on prevention, diagnosis, and treatment receive much less support.)
Palmer contends that, despite manifesting in many different ways, all mental illnesses might stem from a single underlying disorder. He gives three reasons why the complexity of mental illnesses actually points to a common cause.
1. Shared features among disorders: Many mental illnesses, even though they’re listed as separate disorders in the DSM, share common symptoms, risk factors, and ways of treatment. For instance, some medicines work for both depression and anxiety. This hints that these illnesses may not be as different as we assume.
(Shortform note: Studies show that genes related to various mental disorders often overlap, leading scientists to introduce the idea of a p factor (general psychopathology factor). This factor represents a person’s overall risk for mental health problems—not just for one disorder. For example, many genes are associated with both bipolar disorder and schizophrenia, conditions previously thought to be separate. This genetic connection extends to other mental health disorders like depression, anxiety, and ADHD, suggesting a broader link among these disorders.)
2. A rise in all kinds of mental disorders: Mental illness is a growing problem, with the World Health Organization (WHO) estimating in 2017 that nearly 800 million people were affected worldwide. But it’s not just one disorder that’s increasing—research shows an increase in different mental disorders like depression, ADHD, and schizophrenia. This increase across the board suggests a common underlying factor.
(Shortform note: As of 2019, the WHO reports that the number of people with a mental disorder worldwide has reached 970 million. Some experts argue that the apparent rise in mental disorders may be partly due to increased awareness and reporting rather than an increase in prevalence. They suggest that mental health awareness campaigns have reduced stigmas and improved mental health literacy, which is leading more people to recognize and report symptoms.)
3. Individuals often suffer from more than one mental disorder: Research shows that, if you have one mental disorder, you’re more likely to get another. Palmer writes that about half of the people with one mental disorder have one or more additional disorders, a situation known as comorbidity, which hints at a relationship between different mental disorders.
(Shortform note: This high rate of comorbidity has led to the rise of the transdiagnostic approach in mental health treatment. Instead of treating each disorder separately, transdiagnostic treatments try to address several disorders at once by targeting common underlying factors that contribute to various mental health problems. This approach has several potential benefits: It may reduce overall treatment time and cost and help therapists consider all the important factors affecting a patient’s mental health instead of just those related to a single diagnosis.)
4. A connection between mental disorders and metabolic diseases. Palmer points out that people with mental illnesses often have metabolic issues, which include conditions like obesity, diabetes, and heart disease. This suggests that mental health disorders and metabolic diseases are also linked.
(Shortform note: The idea that the mind and the body are connected isn’t a new theory. In When the Body Says No, Gabor Maté argues that modern medicine’s dualistic view, which separates mental and physical health, is flawed. He advocates a holistic approach that considers the biological, psychological, and social factors involved in disease and treats the patient as a whole. The link Palmer notes between mental disorders and metabolic disease supports Maté’s view that we cannot treat the mind as separate from the body.)
According to Palmer’s brain energy theory, mental disorders are caused by metabolic issues. Metabolism is the process that converts food into energy, keeping your cells healthy and allowing your body to grow, maintain itself, and get rid of waste. If your metabolism malfunctions, the energy in your body gets disrupted, and depending on where this malfunction occurs, you might experience a range of mental and physical symptoms. Palmer notes that your brain consumes about 20% of the energy your body produces, which makes it highly reactive to imbalances in the amount of energy it receives.
